Search Images Maps Play YouTube News Gmail Drive More »
Sign in
Screen reader users: click this link for accessible mode. Accessible mode has the same essential features but works better with your reader.

Patents

  1. Advanced Patent Search
Publication numberUS5235286 A
Publication typeGrant
Application numberUS 07/698,012
Publication dateAug 10, 1993
Filing dateMay 9, 1991
Priority dateJun 12, 1985
Fee statusPaid
Also published asDE3687819D1, DE3687819T2, EP0222013A1, EP0222013A4, EP0222013B1, US5101657, WO1986007483A1
Publication number07698012, 698012, US 5235286 A, US 5235286A, US-A-5235286, US5235286 A, US5235286A
InventorsMichael Masia, James P. Reed, Robert S. Wasley, Larry R. Reeder, Peter L. Brooks, Thomas W. Tolles, Louis M. Frank, Mauro Bonomi, Ray F. Stewart, John Lahlough, Lawrence Welsh
Original AssigneeRaychem Corporation
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Method for detecting and obtaining information about changers in variables
US 5235286 A
Abstract
An elongate sensor for detecting and locating presence of a liquid, e.g. water or a hydrocarbon. The sensor includes first and second elongate members which are spaced apart from each other and each of which is a metal conductor covered by a conductive polymer; a third, insulated elongate conductor; and an elongate insulating core. At least one of the elongate members is helically wrapped around the core. Presence of the liquid at any point along the length of the sensor causes the first and second members to be electrically connected at that point, creating a system in which the potential drop down one of the members can be measured and the location of the connection determined.
Images(5)
Previous page
Next page
Claims(12)
We claim:
1. An elongate sensor for use in a method for detecting and locating the presence of a liquid, the sensor comprising
(1) a first elongate electrical connection means
(i) which has a near end and a far end; and
(ii) which comprises an elongate metal core electrically surrounded by a jacket of a conductive polymer composition which comprises a polymeric component and, dispersed in the polymeric component, a sufficient amount of a particulate conductive filler to render the composition conductive at ambient temperature;
(2) a second elongate electrical connection means
(i) which has a near end adjacent the near end of the first connection means and a far end adjacent the far end of the first connection means,
(ii) which comprises an elongate metal core electrically surrounded by a jacket of a conductive polymer composition which comprises a polymeric component and, dispersed in the polymeric component, a sufficient amount of a particulate conductive filler to render the composition conductive at ambient temperature;
(iii) whose resistance, from the near end to each point thereon, is characteristic of its length from the near end to that point, and
(iv) which is electrically insulated from the first connection means between its near end and its far end in the absence of the liquid and which, in the presence of the liquid, becomes electrically connected to the first connection means, the connection being effective at a first point whose location is defined by the location of the point or points at which the liquid is present;
(3) a third elongate electrical connection means
(i) which has a near end adjacent the near ends of the first and second connection means and a far end adjacent the far ends of the first and second connection means, and
(ii) which is an insulated wire which is electrically insulated from said first and second electrical connection means between its near end and its far end in the absence of the fluid and in the presence of the fluid; and
(4) an elongate insulating core;
the first, second and third connection means being physically secured together; and at least one of the first, second and third connection means being spirally wrapped around the core at a constant pitch.
2. A sensor according to claim 1 which is suitable for use in a method for detecting and locating the presence of a liquid electrolyte and in which each of the first and second connection means comprises a continuously exposed conductive polymer surface so that the presence of an electrolyte at any point along the length of the sensor results in electrical connection between the first and second connection means through the electrolyte at that point.
3. A sensor according to claim 2, wherein the first and second connection means are substantially parallel to each other and are helically wrapped at a constant pitch around the insulating core, the first and second connection means thus providing alternate turns of a double helix.
4. A sensor according to claim 3 which includes a fourth elongate electrical connection means which
(i) has a near end adjacent the near ends of the first, second and third connection means and a far end adjacent the far ends of the first, second and third connection means, and
(ii) is a wire which is electrically insulated from the first, second and third connection means between its near end and its far end (a) in the absence of the electrolyte and (b) in the presence of the electrolyte;
and wherein the first, second, third and fourth connection means are substantially parallel to each other rand are helically wrapped at a constant pitch around the insulating core.
5. A sensor according to claim 1 which is suitable for use in a method for detecting and locating the presence of a liquid hydrocarbon and which comprises an elongate swellable member and an elongate restraining member which surrounds the swellable member, the swellable member, in the presence of a liquid hydrocarbon, swelling and thus causing an electrical connection to be made between the first and second electrical connection means.
6. A sensor according to claim 5 wherein the first and second connection means are substantially parallel to each other and are helically wrapped at a constant pitch around the insulating core, the first and second connection means thus providing alternate turns of a double helix.
7. A sensor according to claim 6 which includes an elongate insulating spacer member which is helically wrapped around the core between the first and second connection means and which at all points projects outwardly from the core a greater distance than at least one of the first and second connection means.
8. A sensor according to claims 1, 2, 3, 4, 5, 6 or 7 wherein the insulating core is cylindrical and comprises at least two channels extending along its length, the first connection means being positioned in one of the channels and the second connection means being positioned in another of the channels, and the depth of each of said channels being greater than the diameter of the connection means contained therein.
9. A method for detecting and locating the presence of an electrolyte, which method comprises
(A) providing a system
(a) which comprises
a power source;
a voltage-measuring device; and
an elongate sensor for detecting sand locating the presence of an electrolyte, the sensor comprising
(1) a first elongate electrical connection means
(i) which has a near end and a far end; and
(ii) which comprises an elongate metal core electrically surrounded by a jacket of a conductive polymer composition which comprises a polymeric component and, dispersed in the polymeric component, a sufficient amount of a particulate conductive filler to render the composition conductive at ambient temperature;
(2) a second elongate electrical connection means
(i) which has a near end adjacent the near end of the first connection means and a far end adjacent the far end of the first connection means,
(ii) which comprises an elongate metal core electrically surrounded by a jacket of a conductive polymer composition which comprises a polymeric component and, dispersed in the polymeric component, a sufficient amount of a particulate conductive filler to render the composition conductive at ambient temperature;
(iii) whose resistance, from the near end to each point thereon, is characteristic of its length from the near end to that point, and
(iv) which is electrically insulated from the first connection means between its near end and its far end in the absence of the electrolyte and which, in the presence of the electrolyte, becomes electrically connected to the first connection means, the connection being effective at a first point whose location is defined by the location of the point or points at which the electrolyte is present;
(3) a third elongate electrical connection means
(i) which has a near end adjacent the near ends of the first and second connection means and a far end adjacent the far ends of the first and second connection means, and
(ii) which is an insulated wire electrically insulated from said first and second electrical connection means between its near end and its far end in the absence of the electrolyte and in the presence of the electrolyte; and
(4) an elongate insulating core;
the first, second and third connection means being physically secured together, and at least one of the first, second and third connection means being spirally wrapped around the insulating core at a constant pitch; and
(b) in which system, when an electrolyte is present,
electrical connection is made between the first connection means and the second connection means through said conductive polymer composition;
the connection to the second connection means being effective at a first point whose location is defined by the location of the point or points at which the liquid is present;
the making of the connection resulting in the formation of a test circuit which comprises (i) that part of the second connection means which lies between the first point and a second point at the near end of the second connection means, (ii) the connection, and (iii) the power source, the power source causing an electrical current of known size to be transmitted between the first and second points on the second connection means; and
the current and the second connection means being such that, by measuring the voltage drop between the first and second points, the spatial relationship between the first and second points can be determined;
(B) monitoring the system continuously or on a schedule to determine when a said connection has been made, said test circuit being in existence while said monitoring is taking place if a said connection has been made;
(C) when it is determined that a said connection has been made, using the voltage-measuring device to determine the voltage drop between the first and second points; and
(D) obtaining the location of the first point from the measurement made in step (C).
10. A method according to claim 9 wherein
(1) said electrical connection between the first and second connection means can be made at any point along the length of the sensor,
(2) the second connection means has an impedance Ztotal between its near end and its far end, and
(3) the test circuit includes a component which (i) is connected in series with that part of the second connecting means which lies between the first point and the second point, and (ii) has an impedance substantially equal to the difference between Ztotal and the impedance of that part of the second connection means which lies between the first point and the second point.
11. A method according to claim 9 wherein
(1) in the test circuit, the power source has an output voltage V volts and causes an electrical current I amps of known size to be transmitted between the first and second points on the second connection means; and
(2) when the value of the ratio V/I is within a predetermined range, but not when said ratio is outside said predetermined range, the location of the first point is obtained from the voltage drop between the first and second points.
12. A method according to claims 9, 10 or 11 wherein
(1) said system includes a reference impedance which has a known impedance;
(2) the test circuit includes the reference impedance;
(3) the electrical current which is transmitted between the first and second points in the test circuit has a known relationship with the current which is transmitted through the reference impedance in the test circuit; and
(4) the current, the reference impedance and the locating member are such that, by obtaining a ratio between a first voltage drop across the reference impedance and a second voltage drop between the first and second points on the locating member, the spatial relationship between the first and second points can be determined.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of Ser. No. 372,179 filed Jun. 27, 1989, now U.S. Pat. No. 5,015,958, which is a continuation of Ser. No. 306,237, filed Feb. 2, 1989, now abandoned, which is a continuation of Ser. No. 832,562 filed Feb. 20, 1986, now abandoned, which is a continuation-in-part of each of the following commonly assigned applications:

(1) Ser. No. 599,047 filed Apr. 11, 1984, by Masia and Reed, now abandoned, which is a continuation-in-part of Ser. No. 509,897, filed Jun. 30, 1983, by Masia and Reed, now abandoned;

(2) Ser. No. 556,740, filed Nov. 30, 1983, by Wasley, now abandoned;

(3) Ser. No. 556,829, filed Dec. 1, 1983, by Wasley, now abandoned, which is a continuation-in-part of Ser. No. 556,740, now abandoned;

(4) Ser. No. 618,109, filed Jun. 7, 1984, by Reeder, now abandoned;

(5) Ser. No. 618,108, filed Jun. 7, 1984, by Brooks and Tolles, now abandoned, which is a continuation-in-part of Ser. No. 603,485, filed Apr. 24, 1984, by Brooks and Tolles, now abandoned;

(6) Ser. No. 603,484, filed Apr. 24, 1984, by Frank and Bonomi, now abandoned;

(7) Ser. No. 744,170, filed Jun. 12, 1985, by Stewart, Lahlouh and Wasley, now abandoned; and

(8) Ser. No. 787,278, filed Oct. 15, 1985, by Stewart, Lahlouh, Wasley, Hauptly and Welsh, which is a continuation-in-part of Ser. No. 744,170, and which is now abandoned in favor of continuation-in-part Ser. No. 838,725, filed Mar. 11, 1986 now U.S. Pat. No. 4,926,165.

The disclosure of each of the patents and applications referred to above is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to methods and apparatus for detecting and locating the presence of liquids.

2. Introduction to the Invention

A number of methods have been used (or proposed for use) to detect a liquid leak. Many of these methods make use of two detector members which are insulated from each other in the absence of the liquid but which become electrically connected when the liquid is present. When the liquid to be detected is water or another electrolyte, the detector members may be wires which are continuously or intermittently exposed, so that when an electrolyte is present, the detector members are electrically connected to each other through the electrolyte--see for example U.S. Pat. No. 3,098,116 (Jore et al), especially FIGS. 2 and 3, and U.S. Pat. No. 4,319,232 (Westphal et al), especially FIGS. 2, 3, and 4. When the liquid to be detected is a hydrocarbon, the sensor may comprise a member which swells when it is contacted by the hydrocarbon and which thus causes the detector members to become electrically connected--see for example U.S. Pat. No. 3,470,340 (Hakka). Some of the known methods make use of elongate sensors which not only signal when the leak takes place, but also indicate the location of the leak. For this purpose, the sensor may include a third, fully insulated wire which can form part of an electrical bridge circuit including the leak connection--see for example U.S. Pat. No. 3,365,661 (Zimmerman), especially FIGS. 2 and 3.

SUMMARY OF THE INVENTION

This invention relates to sensors in which each of the detector members is a metal core surrounded by a conductive polymer, and in which one or more of the electrically operative elements of the sensor are wrapped around an insulating core. The invention also relates to improved electrical systems for use in the detection and location of liquid leaks.

In its first aspect, this invention provides an elongate sensor for use in a method for detecting and locating the presence of a liquid, the sensor comprising

(1) a first elongate electrical connection means (often referred to herein as the source member)

(i) which has a near end and a far end; and

(ii) which comprises an elongate metal core electrically surrounded by a jacket of a conductive polymer composition which comprises a polymeric component and, dispersed in the polymeric component, a sufficient amount of a particulate conductive filler to render the composition conductive at ambient temperature;

(2) a second elongate electrical connection means (often referred to herein as the locating member)

(i) which has a near end adjacent the near end of the first connection means and a far end adjacent the far end of the first connection means,

(ii) which comprises an elongate metal core electrically surrounded by a jacket of a conductive polymer composition which comprises a polymeric component and, dispersed in the polymeric component, a sufficient amount of a particulate conductive filler to render the composition conductive at ambient temperature;

(iii) whose resistance, from the near end to each point thereon, is characteristic of its length from the near end to that point, and

(iv) which is electrically insulated from the first connection means between its near end and its far end in the absence of the liquid and which, in the presence of the liquid, becomes electrically connected to the first connection means, the connection being effective at a first point whose location is defined by the location of the point or points at which the liquid is present;

(3) a third elongate electrical connection means (often referred to herein as the return member)

(i) which has a near end adjacent the near ends of the first and second connection means and a far end adjacent the far ends of the first and second connection means, and

(ii) which is a wire which is electrically insulated from said first and second electrical connection means between its near end and its far end in the absence of the fluid and in the presence of the fluid; and

(4) an elongate insulating core;

the first, second and third connection means being physically secured together; and at least one of the first, second and third connection means being spirally wrapped around the core at a constant pitch. The insulating core can be provided by insulation surrounding the third elongate electrical connection means or by a separate member.

In its second aspect, this invention provides a method for detecting and locating the presence of a liquid, particularly an electrolyte, which method comprises

(A) providing a system

(a) which comprises

a power source;

a voltage-measuring device; and

an elongate sensor as defined above, and

(b) in which system, when the fluid to be detected is present,

electrical connection is made between the first connection means and the second connection means through said conductive polymer composition;

the connection to the second connection means being effective at a first point whose location is defined by the location of the point or points at which the liquid is present;

the making of the connection resulting in the formation of a test circuit which comprises (i) that part of the second connection means which lies between the first point and a second point at the near end of the second connection means, (ii) the connection, and (iii) the power source, the power source causing an electrical current of known size to be transmitted between the first and second points on the second connection means; and

the current and the second connection means being such that, by measuring the voltage drop between the first and second points, the spatial relationship between the first and second points can be determined;

(B) monitoring the system continuously or on a schedule to determine when a said connection has been made, said test circuit being in existence while said monitoring is taking place if a said connection has been made;

(C) when it is determined that a said connection has been made, using the voltage-measuring device to determine the voltage drop between the first and second points; and

(D) obtaining the location of the first point from the measurement made in step (C).

BRIEF DESCRIPTION OF THE DRAWING

The invention is illustrated in the accompanying drawing, in which

FIGS. 1-7 are diagrammatic illustrations of sensors of the invention, and

FIGS. 8-11 are circuit diagrams illustrating the methods of the invention.

DETAILED DESCRIPTION OF THE INVENTION

In describing the invention, the first connection means is often referred to as the source member (since it is, in use, connected to the power source); the second connection means is often referred to as the locating member (since the voltage drop between the first and second points thereon is used to calculate the location of the leak); and the third connection means is often referred to as the return member (since it provides a return leg in the circuit created by the leak connection).

Each of the source, locating and return members is elongate, this term being used herein to denote a member having a length which is substantially greater, e.g. at least 100 times greater, often at least 1,000 times greater, sometimes at least 10,000 greater or even at least 100,000 times greater, than either of its other dimensions.

In many cases, it is convenient for one, two or all three of the locating, return and source members to comprise simple conductors which are of constant cross-section and which have resistance but no reactance. The locating, return and source members can be the same or different, but it is convenient, for making splices between sensors at intermediate points, if the locating and source members are identical.

The locating member preferably has an impedance such that the voltage drop between the first and second points is sufficiently high to be easily and accurately measured, but not so high as to require a large power source. Preferably, therefore, it has a resistance of at least 0.1 ohm/ft, particularly at least 1 ohm/ft, but less than 20 ohm/foot, e.g. 1 to 5 ohm/foot. So that the accuracy of the results is not adversely affected by changes in the ambient temperature, the metal in the core of the locating member is preferably one having a temperature coefficient resistivity of less than 0.003, particularly less than 0.0003, especially less than 0.00003, per degree Centigrade over the temperature range 0 to 100 C., for example Constantan (also known as Eureka), Manganin or Copel.

Each of the locating the source members comprises an elongate metal core which is electrically surrounded by a conductive polymer. The conductive polymer jacket helps these members to withstand the stresses on them during installation and use, even when the metal core is a wire of relatively small cross-section. The term "electrically surrounds" is used herein to mean that all electrical paths to the metal core (intermediate the ends thereof) pass through the jacket. Normally the conductive polymer will completely surround the core, being applied for example by a melt-extrusion process; however, it is also possible to make use of a jacket which has alternate insulating sections and conductive sections. The conductive polymer not only provides physical strength but also prevents corrosion of the metal core.

The term "conductive polymer" is used herein to denote a composition which comprises a polymeric component (e.g. a thermoplastic or an elastomer or a mixture of two or more such polymers) and, dispersed in the polymeric component, a particulate conductive filler (e.g. carbon black, graphite, a metal powder or two or more of these). Conductive polymers are well known and are described, together with a variety of uses for them, in for example U.S. Pat. Nos. 2,952,761; 2,978,665; 3,243,753; 3,351,882; 3,571,777; 3,757,086; 3,793,716; 3,823,217; 3,858,144; 3,861,029; 4,017,715; 4,072,848; 4,117,312; 4,177,446; 4,188,276; 4,237,441; 4,242,573; 4,246,468; 4,250,400; 4,255,698; 4,271,350; 4,272,471; 4,304,987; 4,309,596; 4,309,597; 4,314,230; 4,315,237; 4,317,027; 4,318,881; 4,330,704; 4,388,607; and 4,426,339. The disclosure of each of these patents is incorporated herein by reference.

The resistivity of conductive polymers usually changes with temperature at a rate well above the preferred temperature coefficient of resistivity set out above. Accordingly it is preferred that at all temperatures from 0 to 100 C., each longitudinal section of the conductive polymer jacket has a resistance which is at least 100 times, preferably at least 1000 times, the resistance of the core of that longitudinal section. In this way (since the core and the jacket are connected in parallel), the jacket does not make any substantial contribution to the resistance of the elongate conductor, and any change in its resistance with temperature is unimportant.

The source, location and return members are physically secured together (so that they follow the same elongate path), and at least one of them is spirally wrapped around an elongate insulating core at a constant pitch. Since the return member is completely insulated, the insulation of the return member can provide the insulating core, with the source and locating members being wrapped around it. Alternatively, the insulating core can be a separate member. Preferably, the source and locating members are substantially parallel to each other and are helically wrapped at a constant pitch around the insulating core, thus providing alternate turns of a double helix.

In one embodiment, the source and locating members are separated from each other by an insulating spacer which lies between them and which is separable from each of them and from the core. Such a spacer can be wrapped around the core at the same time as the source and locating members. In another embodiment, the source and locating members are separated by an insulating jacket on one or both of the members; when the sensor is to be used to detect an electrolyte, the jacket(s) must be continuously or intermittently apertured to permit the electrolyte to contact both the members. In another embodiment, the insulating core comprises depressions into which one of the conductive members is fitted. For example, the core may be cylindrical and comprise at least two channels extending along its length, with an elongate connection means positioned in each channel. Preferably, each of the channels in the cylindrical core has a depth which is greater than the diameter of the elongate connection means contained in the channel.

The helically wrapped configuration of the novel sensors results in substantial advantages, including in particular:

(a) the ability to produce, from a limited inventory of starting materials, a range of sensors of very different properties, in particular as to resolution (which depends on the impedance, per unit length of the sensor, of the locating member), and as to sensitivity (which often depends on the physical separation of the first and second connection means), by changes in easily adjusted manufacturing variables, e.g. the pitch of the wrapping, the separation of the wrapped components, and the means used to separate the wrapped components;

(b) the ability easily to incorporate into the cable additional elongate electrical means which can be used, for example, for continuity testing or ground fault detection, or so that the test circuit contains a "balancing" components, so that its sensitivity is not dependent on the distance of the leak connection from the near end, as further described below; and

(c) the ability to manufacture a cable having a circular cross-section, so that it is compliant in all planes and is equally sensitive in all planes.

When the sensor is to be used to detect the presence of water or another electrolyte, it is preferred that each of the source and locating members has a continuously exposed conductive polymer surface, so that if an electrolyte is present at any point along the length of the sensor, it fills the space between the locating and source members and produces an electrical connection between the source and locating members through the electrolyte at that point.

When the sensor is to be used to detect the presence of a liquid which is not an electrolyte, e.g. a hydrocarbon, the sensor preferably includes an elongate swellable member and an elongate restraining member, e.g. a braid, which surrounds the swellable member, but through which the liquid can pass. The swellable member, in the presence of the liquid to be detected, swells and thus causes an electrical connection to be made between the source and locating members. The swellable member is preferably a hollow, tubular member which surrounds the source and locating members and contacts at most one of them in the absence of the liquid to be detected. The swellable member can itself be conductive, e.g. be composed of a conductive polymer having a resistivity (before swelling) of 1 to 250 ohm.cm, or its swelling can cause another conductive member to contact both the source and the location members. The conductive member preferably has a low modulus of elasticity, e.g. 1108 to 5109 dynes/cm2, measured at 29 C. at a frequency of 1 radian per second, so that it is easily deformed by the swelling. It can be separated from the source and locating members by an apertured separator, through the apertures of which it is urged by the swelling. The apertured separator may for example comprise a braid of insulating filaments, or it may comprise a helically wrapped insulating member which lies between helically wrapped source and locating members and which extends outwards from the insulating core a greater distance than at least one of the source member and the location member. The separation of the conductive member from the source and/or locating member, in the unactivated sensor, is typically 0.001 to 0.05 inch, e.g. about 0.01 inch.

The swellable member is preferably composed of a polymeric material, preferably one which has been lightly crosslinked, e.g. a styrene-butadiene-styrene block copolymer, a styrene-butadiene elastomer, natural rubber isoprene rubber or nitrile rubber. The polymeric material is selected to swell in the liquid to be detected, but preferably not in any other liquid which might also be present.

Further details of the sensors of the invention are given in the description of FIGS. 1-6 below.

In the method of the invention, the presence of a liquid, preferably water or another electrolyte, causes an electrical connection to be made between the locating and source members at a first point. A current of known size is driven through the electrical connection and down the locating member to a second point at the near end of the locating member. The voltage drop between the first and second points is measured and the location of the first point can then be determined.

When the liquid causes a single or very short connection to be made between the locating and source members, then the "first point" will of course be easily identified. However, when the liquid results in connection at two or more spaced-apart locations and/or over a finite length of the locating member, the "first point", i.e. the point whose location can be determined from the observed voltage drop, is some intermediate point which can conveniently be referred to as the "electrical center" of the various connections. If there are connections at two or more spaced-apart locations, the "electrical center" may be at a location at which there is no connection between the locating and source members. It is for this reason that the connection to the locating member is sometimes referred herein as being "effective" at the first point. However, it is to be understood that where reference is made herein to the connection being "made" at the first point, this is intended to include situations in which a plurality of electrical connections are made between the locating member and the source member, with the electrical center of the connections being at the first point.

An important advantage of the method of the invention, especially when the connection is made through an electrolyte, is that the information obtained about the location of the liquid can be independent of the impedance of the connection to the locating member, i.e. the information obtained remains the same even if a substantial and unknown change is made in the impedance of the connection.

Further details of the method of the invention are given in the description of the preferred embodiments and in the description of FIGS. 7-10 below.

In a preferred embodiment of the method of the present invention,

(1) the electrical connection between the source and locating members can be made at any point along the length of the sensor,

(2) the second connection means, i.e. the locating member, has an impedance Ztotal between its near end and its far end, and

(3) the test circuit includes a "balancing" component which (i) is connected in series with that of the second connection means which lies between the first point and the second point, and (ii) has an impedance substantially equal to the difference between Ztotal and the impedance of that part of the second connection means which lies between the first point and the second point.

The use of such a balancing component solves the problem that the system is otherwise more sensitive at the near end, adjacent to the power supply, than at the far end, since the total impedance of the test circuit varies with the location of the first point. The balancing component is preferably provided by using identical first and second connection means, and by including in the sensor a fourth elongate electrical connection means which

(i) has a near end adjacent the near ends of the first, second and third connection means and a far end adjacent the far ends of the first, second and third connection means, and

(ii) is a wire which is electrically insulated from the first, second and third connection means between its near end and its far end (a) in the absence of the liquid and (b) in the presence of the liquid;

The first, second, third and fourth connection means are preferably substantially parallel to each other and are helically wrapped at a constant pitch around the insulating core. The fourth connection means, when the sensor forms part of an operating system using the method of the invention, is connected at its near end to the power source and at its far end to the far end of the source member, so that the balancing component is provided by that part of the source member which lies between the connection and the far end. Further details are given below in connection with FIG. 8.

In another preferred embodiment of the method of the invention, the system operates to locate the first point only when the connection between the source and locating members has an impedance within a predetermined range. In this embodiment,

(1) in the test circuit, the power source has an output voltage V volts and causes an electrical current I amps of known size to be transmitted between the first and second points on the second connection means; and

(2) when the value of the ratio V/I is within a predetermined range, but not when said ratio is outside said predetermined range, the location of the first point is obtained from the voltage drop between the first and second points.

This method is particularly useful when the power source is a controlled current source delivering a "fixed" current, and the connection is caused by the presence of an electrolyte. Under such circumstances, if only a very small amount of electrolyte is present, so that the locating and source members are connected to each other through a connection whose resistance is very high, false information may be provided, because the "controlled current" source cannot supply the expected current because its compliance voltage is insufficient to drive the "fixed" current in the test circuit. Under such circumstances, this embodiment can be used to prevent the delivery of information if the current falls below the "fixed" value. Further details are given below in connection with FIG. 9.

In another preferred embodiment of the method of the invention,

(1) said system includes a reference impedance which has a known impedance;

(2) the test circuit includes the reference impedance;

(3) the electrical current which is transmitted between the first and second points in the test circuit has a known relationship with the current which is transmitted through the reference impedance in the test circuit; and

(4) the current, the reference impedance and the locating member are such that, by obtaining a ratio between a first voltage drop across the reference impedance and a second voltage drop between the first and second points on the locating member, the spatial relationship between the first and second points can be determined.

A particular advantage of such modified systems is that variation in the size of the current do not have an adverse effect on the accuracy with which the location of the liquid can be calculated. As a result, the power supply need not be a constant current source, and the minor variations which occur even in a "constant" current source, do not matter. Further details are given below in connection with FIG. 10.

Reference will now be made to the Drawings.

FIG. 1 is a diagrammatic cross-section through a sensor which is suitable for detecting the presence of an electrolyte and which has been made by braiding a first connection means (comprising a metal, e.g. copper, core 1 and a conductive polymer jacket 5), a parallel second connection means (comprising a metal, e.g. "Copel", core 2 and a conductive polymer jacket 6) and ten elongate insulating members 11 around an insulating core which is provided by an insulating jacket 4 which surrounds a third connection means 3 in the form of a metal, e.g. copper, wire. It should be noted, however, that the distance between the center of the sensor and the various braided elements will not be constant as shown in the Figure, but will change as the elements interlace with each other, and that the various cross-over points between the elongate elements are not shown.

FIGS. 2 to 5 illustrate sensors which are suitable for use in the detection of hydrocarbons.

FIG. 2 shows a sensor which comprises a first connection means (comprising a metal core 1 and a conductive polymer jacket 5), and a parallel second connection means (comprising a metal core 2 and a conductive polymer jacket 6) which are helically wrapped around an insulating core provided by an insulating jacket 4 which surrounds a third connection means 3 in the form of a metal, e.g. copper, wire. A braid 12 composed of polyvinylidene fluoride filaments surrounds the first and second connection means and the core, and is in turn surrounded by a tubular swellable member 14 which is composed of a styrene-isoprene-styrene block copolymer having carbon black dispersed therein and which swells when exposed to a hydrocarbon. Swellable member 14 is surrounded by a restraining member 16 composed of braided glass fibres.

FIGS. 3 and 4 show the sensor of FIG. 2 before and after swelling of member 14 respectively. As can be seen in FIG. 3, before swelling, separator braid 12 prevents electrical contact between the first and second connection means. After swelling (FIG. 4) the swollen member 14, prevented from swelling outwards by the braid 16, has penetrated through the braid 12 and thus provided a conductive bridge between the first and second connection means.

FIG. 5 shows a sensor similar to that shown in FIGS. 2 and 4 in which the swellable conductive member 14 is replaced by a hollow swellable, non conductive member 18 and a hollow non-swellable conductive member 20. The swellable member 18 surrounds the conductive member 20, and on swelling urges the conductive member 20 through the separator braid 12.

FIG. 6 shows another sensor for detecting hydrocarbons. First and second connection means as in FIG. 2 (1, 5 and 2, 6) are helically wrapped around a central elongate support core provided by the insulating jacket 4 which surrounds third connection means 3 in the form of a metal wire. Two insulating spacer wires 40, 42 are also helically wrapped around the support core, in the same sense as, and lying between, the first and second connection means. Four filler wires 44 and also helically wrapped around the support core, in the opposite sensor, so that they pass over but not under the first and second connection means, and both over and under the spacer wires 40, 42. A tubular, swellable, conductive polymer member 14 surrounds the support core and the elongate members wrapped around it. The spacer wires 40 have a larger diameter than the first and second connection means, and thus separate the first and second connection means from the tubular conductive swellable member 14. When the swellable member is exposed to a hydrocarbon, it swells, contacts and bridges the first and second connection means, forming an electrical path therebetween.

FIG. 7 is a cross-section through a part of a sensor according to the invention. An insulating cylindrical core 52 contains two channels 54 extending along its length. A first connection means (comprising a metal core 1 and a conductive polymer jacket 5) lies in one of the channels 54, and a second connection means (comprising a metal core 2 and a conductive polymer jacket 6) lies in the other channel 54. The diameter of these connection means is smaller than the depth of the channels 54.

FIG. 8 shows the electrical circuit which is present when the simplest embodiment of the method of the invention is being used to locate a liquid leak. The near end of a source member 12 is electrically connected, through a constant current source 15, to the near end 2 of a locating member 11. A return member 16 is connected at its near end, through a voltmeter 14, to the near end 2 of the locating member 11, and at its far end to the far end of the locating member 11. The presence of a liquid has caused an electrical connection E to be made between the source member 12 and a first point 1 on the locating member 11, thus forming a test circuit which includes the connection, the locating member between points 1 and 2, the constant current source 15 and part of the source member. The current supplied by the power source 15 is preferably 0.1 to 10 milliamps, e.g. 0.5 to 3 milliamps. In addition, there is a reference circuit which comprises the voltmeter 14, the locating member 11 and the return member 16.

It will be seen that the location of point 1 can be calculated if the following are known:

(a) the current flowing between points 1 and 2,

(b) the impedance of the components of the reference circuit,

(c) the voltage drop measured by the voltage-measuring device, and

(d) the impedance of the locating member between point 2 and each point on the locating member.

The accuracy with which the first point can be located is limited by the ratio of the impedance of the voltmeter to any unknown part of the impedance of the other components of the reference circuit. Preferably, therefore, the voltmeter has a resistance of at least 1 megohm, especially at least 10 megohms, and the ratio of the impedance of the voltmeter to the total impedance of the rest of the reference circuit is at least 1,000, especially at least 10,000. By contrast, the resistance of the connection between the locating and source members, and the resistance of the other components of the test circuit, do not affect the accuracy of the information obtained, provided that the power source 15 can deliver its rated constant current.

FIG. 9 is the same as FIG. 8 except that the far end of the source member 12 is connected to the power source 15 via an auxiliary member 13, so that the test circuit includes the auxiliary member 13 and that part of the source member 12 which lies between the connection and the far end instead of that part of the source member 12 which lies between the connection and the near end of the source member. In addition, the source and locating members are made from the same metal core and conductive polymer jacket. As a result, the test circuit has an impedance which is fixed except for the impedance of connection E. The sensitivity of the system is, therefore, independent of the location of the connection E. In addition, it is possible to select precisely the limits of the impedance of the connection E which will cause the system to signal that a leak has taken place, as further described below.

FIG. 10 is similar to FIG. 8 but includes also an overrange blanking unit 22 and a display unit 20, which displays the location of the connection E. The blanking unit 22 monitors the output voltage of the constant current source 15, and if the output voltage exceeds the compliance voltage (in which case the current in the test circuit will be below the expected constant current value), blanks out the display (which will be wrong, because it is calculated on the basis of the "constant" current).

FIG. 11 is similar to FIG. 8, but includes also a reference resistor 25 which is connected in series with the locating member, and a second voltmeter 26, which measures the voltage drop over the reference resistor 25. The outputs of the two voltmeters 16 and 26 are fed to a divider 27 which compares them, calculates the location of the connection and feeds the results of the calculation to a display 20. It is important that the reference impedance has a known, fixed value under the conditions of operation. Accordingly, the reference impedance preferably has a temperature coefficient of impedance which averages less then 0.003 per degree C. over the temperature range 0 to 100 C. The reference impedance preferably has resistance and no reactance. Typically values are 0.1 to 10 times, e.g. 0.5 to 2 times, the resistance of the full length of the location member. The system can include two or more reference impedances and switching means for selecting one or more of the reference impedances.

The invention is illustrate by the following Examples.

EXAMPLE 1

A circuit as shown in FIG. 6 was prepared. The controlled current source was a galvanostat with a compliance voltage of 18 volts and produced a controlled current of 0.001 amp. The voltmeter had an input impedance of 1 megohm and a full scale reading of 200 mV. The source member was a 30 AWG copper wire which was surrounded by a melt-extruded jacket of a conductive polymer composition. The jacket was about 0.04 inch thick. The conductive polymer composition has a resistivity of about 3 ohm.cm at 25 C. and comprised carbon black (about 45 part by weight) dispersed in a thermoplastic rubber which is sold under the trade name TPR-5490 and which is believed to be a blend of polypropylene and an ethylene/propylene rubber (about 55 parts by weight). The locating member was the same as the source member except that a 30 AWG Constantan wire was used instead of the copper wire. The resistance of the locating conductor was 2.940 ohms/foot. The return member was a 12 AWG copper wire and it was surrounded by a polymeric insulating jacket.

In a number of tests, a damp sponge was placed on the locating and source members to effect electrical connection between them, the members being dried between the tests. It was found that, as expected from theory, the distance (d) in feet to the damp sponge could be calculated from the equation ##EQU1## where V is the voltage (in volts) recorded by the voltmeter. The discrepancy between the actual and calculated values of d was less than 0.1%.

EXAMPLE 2

Two conductive members, the first comprising a copper core surrounded by a conductive polymer jacket and the second comprising a "Copel" core surrounded by a conductive polymer jacket, together with insulating members, were formed into a braid around an insulating jacket surrounding a third copper stranded wire. An insulating jacket comprising polyvinylidenefluoride fibres was then braided thereover.

A swellable conductive polymer composition was compounded using a Banbury mixer. The composition had the following composition:

______________________________________Kraton 1107         58.0   weight %Conductex 975       35.0Shellflex 371       5.0TAIC                1.0Irganox 1010        0.5Agerite Resin D     0.5               100.0______________________________________Kraton 1107      is a styrene-isoprene-styrene block copolymer      manufactured by Shell Chem. Co. with a      styrene/rubber ratio of 28/72.Conductex 975      is a high surface area carbon black with high      electrical conductivity manufactured by Cities      Service Company, Columbian Division.Shellflex 371      is a naphthenic oil manufactured by Shell Oil      and is used as a processing aid.TAIC       is triallylisocyanurate, which is a radiation      crosslinking agent.Irganox 1010      are antioxidants/antidegradants/heat stabilizersAgerite Resin D

The swellable conductive composition was extruded over the braid-enclosed cables. The extrudate had a wall thickness in the range 50 to 60 mils, an external diameter of 0.25 inch and an internal diameter of 0.19 inch. The extruded material was beamed with a beam of high energy electrons to a dose of 10 Mrads throughout. Finally the swellable material was overbraided with a restraining braid comprising glass fibre, Fibreglass ECG 105-3/4, as supplied by Owens Corning.

The sensor was then connected into a circuit according to FIG. 7, the "Copel" wire providing the locating member, the copper wire the source member, and the central copper wire the return member. The sensor was immersed in turn in a number of different liquids and the resistance in the test circuit (including the locating and source wires and any connection between them) was monitored. The time (in minutes) for the resistance to fall to 20,000 ohm and further to 1,000 ohm is shown below. Two tests were carried out for each solvent.

______________________________________          TIME to    TIME toLIQUID         20,000 ohms                     1,000 ohms______________________________________JP-7 (Jet Fuel)          8           111/2"              11         16Xylene          31/2       51/2"              2           4Methylethylketone          7          15"              8          19Methylene Chloride          1           41/2"              <1/2        1Acetone        61         114"              105        152Trichlorethylene           11/2       3"              <1         <2Carbon Disulfide          1/2         11/2"              <1/2       1/2______________________________________
EXAMPLE 3

Two devices as shown in FIG. 6 were made. These are referred to as Devices A and B. The sizes of each of the components on devices A and B were as follows:

______________________________________               Device A                       Device B               in Inch in Inch______________________________________Diameter of Support Core (4)                 0.077     0.060Diameter of Spacer Wires (40, 42)                 0.035     0.049Diameter of Conductive Polymer                 0.032     0.032Jackets (5, 6)Diameter of Filler Wires (44)                 0.013     0.013Wall Thickness of Swellable Member (14)                 0.050     0.050______________________________________

Both devices were exposed to solvent to make the swellable member swell and the time for the resistance fall to 20,000 ohm was recorded, as in Example 2. The physical load required to effect the same resistance decrease, in the absence of solvent, was also measured. It is referred to as the load to trigger. The load to trigger was measured by compressing the devices using an Instron machine having a crosshead displacement rate of 0.05 inch per minute. The anvil used to compress the samples had a diameter of 2.25 inches. The load to trigger was calculated per unit length of the device. Two readings were taken in each test. The results are shown below.

______________________________________              Device A                      Device B______________________________________Time in minutes to reduce resistance to                5.0       31.520,000 ohm by solvent                5.0       34.0Load to trigger in lbs. per linear inch                12.5      50.2                15.4      43.5______________________________________

For device A (where the spacer wires project at least 3 mils further than the first and second connection means) the response time is more rapid, but the load to trigger lower, than for device B (where the spacer wires project at least 17 mils further than the first and second connection means). Device A is particularly suited to applications where a rapid response time is required. Device B is particularly suited to applications where the device may be subject to external pressure, and accidental response needs to be avoided.

The load to trigger of device A was increased to over 30 pounds per linear inch by helically wrapping a resilient coil around the device.

For further details of the way in which the novel sensors of this invention can be constructed and used, reference may be made to the parent U.S. Pat. No. 5,015,958, the disclosure of which is incorporated herein for all purposes.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US1084910 *Nov 14, 1911Jan 20, 1914Julius Heinrich Johann Adolpf StephensonMethod for localizing faults in cables and circuits.
US1648197 *Mar 22, 1926Nov 8, 1927Benjamin T RoodhouseWater-operated circuit closer
US1772232 *Dec 6, 1927Aug 5, 1930Guilder Jesse S VanAlarm
US1786843 *Oct 7, 1929Dec 30, 1930Hedeby Hans NLeak detector
US2004569 *May 14, 1926Jun 11, 1935Nat Aniline & Chem Co IncElectrometric determinations
US2360434 *Jul 29, 1943Oct 17, 1944Manning Dennis JLeak-locating apparatus
US2432367 *Sep 23, 1943Dec 9, 1947Wingfoot CorpLeak detector
US2563341 *Nov 30, 1949Aug 7, 1951Gen Motors CorpHumidity control
US2581213 *Dec 15, 1949Jan 1, 1952Gen ElectricTemperature responsive signaling and locating system
US2691134 *Dec 29, 1951Oct 5, 1954Goodyear Tire & RubberLeak detector
US2716229 *Jun 14, 1946Aug 23, 1955Ralph F WehrmannLeak detector
US2741591 *Mar 2, 1951Apr 10, 1956IonicsMethod of and apparatus for separating ions
US2759175 *Mar 12, 1954Aug 14, 1956Spalding Thomas RLeak detector for pipe joint
US2790146 *Apr 2, 1952Apr 23, 1957Honeywell Regulator CoVoltage ratio measuring apparatus
US2841765 *Mar 18, 1955Jul 1, 1958Harrold George BElectric ohmmeter
US2879471 *Feb 23, 1954Mar 24, 1959Dresser IndResistance meter
US2881392 *Jan 10, 1955Apr 7, 1959Western Electric CoD. c. voltage ratio measuring system
US2930232 *Jul 20, 1955Mar 29, 1960Spears Morton FDevice for manifesting thermal boundaries
US2976486 *Jan 16, 1958Mar 21, 1961Daystrom IncResistance comparator
US3033916 *Jun 16, 1958May 8, 1962Insul 8 CorpElectrical conductor
US3045198 *Dec 11, 1959Jul 17, 1962Dolan James PDetection device
US3098116 *Oct 7, 1959Jul 16, 1963Anaconda Wire & Cable CoLeak-detecting telephone cable
US3127485 *Jun 26, 1961Mar 31, 1964Vitolo Robert VRain trigger switch
US3200388 *Aug 12, 1960Aug 10, 1965Weber Aircraft CorpWater leakage alarm system
US3248646 *Jul 19, 1962Apr 26, 1966Whitney Blake CoLocation of cable faults by comparing a section of the faulted cable with a part of the section
US3254334 *Dec 19, 1963May 31, 1966American District Telegraph CoElectrical protection system utilizing reverse polarity line testing with unidirectional current devices having reverse breakdown characteristic
US3304612 *Dec 23, 1963Feb 21, 1967Union Oil CoMethod and apparatus for converting cartograph coordinates to permanent digital form
US3365661 *Apr 26, 1965Jan 23, 1968Anaconda Wire & Cable CoMethod and apparatus for locating leaks in a cable by determining the distance to a short circuit in the cable
US3382493 *Nov 4, 1964May 7, 1968Thermal Conduits IncUnderground pipe insulation liquid-detector
US3383863 *Aug 3, 1966May 21, 1968Joe R. BerryPond, tank and pit liner and method of detecting leaks
US3427414 *Jan 13, 1967Feb 11, 1969Sinclair Research IncSwitch assembly for detecting underground leaks
US3465109 *Oct 25, 1967Sep 2, 1969Sealtronics IncElectrical switch having deformable moving contact arm
US3470340 *Nov 16, 1967Sep 30, 1969Butts Ernest OttoLeak detection apparatus
US3520476 *Jul 19, 1967Jul 14, 1970Schmid Howard CElectronic soil moisture and temperature sensing device
US3550120 *Dec 9, 1968Dec 22, 1970Honeywell IncControl apparatus
US3564526 *Nov 16, 1967Feb 16, 1971Butts Ernest OttoPipeline leak detection device
US3588776 *Jan 13, 1969Jun 28, 1971Lewis Eng CoSafety cable
US3600674 *Apr 2, 1969Aug 17, 1971Chevron ResMethod of determining leaks from buried pipelines using a time-sharing transmission line
US3662367 *Jan 4, 1971May 9, 1972Bell Telephone Labor IncWater alarm and fault-locating for air core plastic-insulated telephone cable
US3702473 *Aug 27, 1971Nov 7, 1972Gen Motors CorpSeven-state resistance sensing supervisory system utilizing single pole-double throw switches
US3706927 *Apr 27, 1971Dec 19, 1972Gustaf I JedvallMethod for measuring the absolute distance to a leakage fault in an electrical conductor
US3721898 *Dec 4, 1968Mar 20, 1973Dragoumis PApparatus for detecting leakage from or rupture of pipes and other vessels containing fluid under pressure
US3800216 *Aug 11, 1971Mar 26, 1974Dynatel CorpCable fault locator apparatus and method with reference voltage comparison
US3800217 *Sep 23, 1971Mar 26, 1974Lowrance Electronics MfgPipeline including means of indicating the existence of and location of a leak
US3812420 *Dec 21, 1972May 21, 1974Gen Ind IncBridge circuit changing fault location method and device
US3849723 *Jun 14, 1973Nov 19, 1974Allen GConductivity measuring method and apparatus
US3852995 *Feb 23, 1973Dec 10, 1974Faberge IncMethod and apparatus for detecting leaks in containers
US3866202 *Oct 29, 1973Feb 11, 1975Gulf & Western Mfg CoAlarm circuitry
US3875331 *Nov 8, 1973Apr 1, 1975Vector GeneralVector tablet digitizing system
US3885097 *Aug 11, 1972May 20, 1975Nat Res DevGraphical input apparatus for electrical apparatus
US3970863 *Dec 13, 1974Jul 20, 1976Sumitomo Chemical Company, LimitedElement and method for detecting leakage of petroleum products
US3981181 *Jul 10, 1975Sep 21, 1976Sadamasa OchiaiMethod for detecting liquid leak and a cable therefor
US3991413 *Jun 23, 1975Nov 9, 1976Berger Philip HConstant current detector system
US4013924 *Mar 19, 1970Mar 22, 1977A/S E. RasmussenMethods and means for detecting the presence of moisture adjacent insulated pipes
US4023412 *Jul 8, 1975May 17, 1977Shell Oil CompanyMethod and apparatus for detecting temperature variation utilizing the Curie point of a ferromagnetic material
US4029889 *Apr 4, 1975Jun 14, 1977Asahi Engineering & Construction Co., Ltd.Fluid-leak detector cable
US4052901 *Jul 29, 1976Oct 11, 1977Bjork Albion PLevel detecting
US4095174 *Jan 18, 1977Jun 13, 1978Towa Electric Co., Ltd.System for detecting leakage faults in a pipeline by measuring the distributed capacitance of sections of a sensing cable buried parallel to said pipeline
US4125822 *Oct 20, 1975Nov 14, 1978Benno PerrenProbe for determining organic liquids
US4129030 *Oct 13, 1977Dec 12, 1978Ads Systems, Inc.Sensing apparatus and method
US4184143 *Jun 1, 1978Jan 15, 1980Texaco Inc.Seismic signal conductor testing system
US4193068 *Apr 4, 1977Mar 11, 1980Ziccardi John JHemorrhage alarms
US4206632 *Jan 23, 1979Jun 10, 1980Hirosuke SuzukiLiquid detecting device
US4224595 *Nov 2, 1978Sep 23, 1980Ads Systems, Inc.Graded particle adsorption type sensor and method of improving performance of an adsorbing sensor
US4237721 *Dec 11, 1978Dec 9, 1980Ads Systems, Inc.Apparatus and method for detecting substances and for regulating current
US4246575 *Feb 2, 1979Jan 20, 1981Purtell Jack LMoisture detector
US4263115 *Jul 3, 1978Apr 21, 1981Max Planck Gesellschaft Zur Forderung Der WissenschaftenUsing ligand-containing membrane
US4278931 *Jan 26, 1979Jul 14, 1981The Post OfficeLocation of contact faults on electrically conductive cables
US4288653 *Mar 17, 1980Sep 8, 1981Blom HDistrict-heating line and a method of manufacturing the same
US4288654 *Mar 17, 1980Sep 8, 1981Blom HDistrict-heating line
US4297686 *Oct 1, 1979Oct 27, 1981Tom M DaleWater detection device
US4298969 *Sep 26, 1979Nov 3, 1981Exxon Production Research CompanyMethod and apparatus for testing the impedances of geophone channels
US4305321 *Oct 10, 1978Dec 15, 1981Cohn James MElectrical control devices
US4307606 *May 16, 1980Dec 29, 1981Johnson Hugh GThermal transition zone sensing and indicating system
US4319078 *Mar 11, 1980Mar 9, 1982Nippon Telegraph & Telephone Public CorporationApparatus for detecting X and Y coordinates of input points
US4319184 *Aug 25, 1980Mar 9, 1982Walter KowalczykRemote control precision step attenuator
US4319232 *Mar 19, 1980Mar 9, 1982Westphal Frank CLiquid leakage detector
US4359721 *Oct 16, 1978Nov 16, 1982American District Telegraph CompanyTwo-wire multi-zone alarm system
US4369436 *May 1, 1981Jan 18, 1983American District Telegraph CompanyAnti-bridging cable supervision circuit
US4374379 *Aug 25, 1980Feb 15, 1983Dennison Jr Everett GMoisture sensing device for pipes and the like
US4386231 *Apr 28, 1981May 31, 1983Canada Wire And Cable LimitedCable assembly for detecting the ingress of water inside a cable
US4400663 *Oct 28, 1981Aug 23, 1983Bell Telephone Laboratories, IncorporatedShunt fault tester for multiconductor cable
US4404516 *Sep 1, 1981Sep 13, 1983Johnson Jr Victor RSystem for detecting leaks from liquid-containing reservoirs and conduits
US4414441 *Apr 2, 1982Nov 8, 1983Emhart Industries, Inc.Hydrocarbon responsive switch
US4423410 *Sep 2, 1982Dec 27, 1983American District Telegraph CompanyTwo-wire multi-zone alarm system
US4424479 *Oct 5, 1981Jan 3, 1984Bell Telephone Laboratories, IncorporatedLoop fault location
US4445012 *Nov 3, 1980Apr 24, 1984Liston Scientific CorporationMoisture sensor for purging system
US4446421 *Jun 22, 1981May 1, 1984Grumman Aerospace CorporationApparatus and method for locating faults in cables
US4449098 *Mar 10, 1981May 15, 1984Osaka Gas Company LimitedArrangement for detecting the location of an electrically insulative continuous item positioned underground
US4467286 *Nov 8, 1982Aug 21, 1984Burr-Brown CorporationResistor ladder network
US4468306 *Apr 6, 1983Aug 28, 1984Dorr-Oliver IncorporatedBiodic electrofiltration
US4468607 *May 4, 1982Aug 28, 1984Sanyo Electric Co., Ltd.Ladder-type signal attenuator
US4503526 *Jul 2, 1982Mar 5, 1985Institut Francais Du PetroleDevice for water inflow detection inside a seismic streamer
US4537668 *Jun 10, 1981Aug 27, 1985Commissariat A L'energie AtomiqueStyrene and polyethylene graft polymerized by irradiation polymerization, dissolving, pouring on support
US4553432 *Jul 11, 1983Nov 19, 1985Reinhold BarlianTemperature-humidity surveillance equipment
US4563674 *Sep 13, 1983Jan 7, 1986Junkosha Company Ltd.Oil leak detector
US4570477 *Jan 27, 1984Feb 18, 1986Junkosha Company Ltd.Leak detecting cable
US4571292 *Aug 12, 1982Feb 18, 1986Case Western Reserve UniversityApparatus for electrochemical measurements
US4594638 *Nov 13, 1984Jun 10, 1986Junkosha Co. Ltd.Liquid leak sensor
US4631952 *Aug 30, 1985Dec 30, 1986Chevron Research CompanyMixtures of electroconductive particles and swellable material
Non-Patent Citations
Reference
1"Water Sentry Leak Sentry Distributed Alarm and Locator Systems", Raychem Corporation, Jan. 1984.
2 *Data Aquisition Handbook, Dec. 1982.
3Stubbings, "Electrical Review", Dec. 28, 1945, p. 947.
4 *Stubbings, Electrical Review , Dec. 28, 1945, p. 947.
5 *Water Sentry Leak Sentry Distributed Alarm and Locator Systems , Raychem Corporation, Jan. 1984.
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US5382908 *Mar 20, 1990Jan 17, 1995Bo Gosta ForsstromConductivity or capacity cell and a method for producing the same and a probe including such a cell and a method for measuring of relative humidity with such a probe
US5410255 *May 7, 1993Apr 25, 1995Perma-Pipe, Inc.Method and apparatus for detecting and distinguishing leaks using reflectometry and conductivity tests
US6538450 *Mar 28, 2001Mar 25, 2003SocratMethod and device for locating an insulation fault in an electric cable
US6777947Apr 29, 2002Aug 17, 2004Tyco Thermal Controls Llc.Sensor cable
US6784371 *Nov 27, 2002Aug 31, 2004Pirelli Kabel Und Systeme Gmbh & Co. KgDetecting substance intrusion in a cable
US6877359 *Nov 30, 2001Apr 12, 2005Taiwan Semiconductor Manufacturing Co., Ltd.Liquid leak detection
US7081759Nov 30, 2004Jul 25, 2006Raymond & Lae Engineering, Inc.Fluid detection cable
US7212009Mar 30, 2006May 1, 2007Raymond & Lae Engineering, Inc.Fluid detection cable
US7755498Aug 10, 2007Jul 13, 2010Tyco Thermal Controls LlcDiscrete leak detection device and method for discriminating the target fluid
US7812734Dec 20, 2007Oct 12, 2010Ken HardinAlarm system employing existing conductive aspect of copper lines as well as optional pressure switch sensor for triggering a copper theft event
US8063309May 12, 2009Nov 22, 2011Raymond & Lae Engineering, Inc.Twisted leak detection cable
US8234910Nov 11, 2010Aug 7, 2012Raymond & Lae Engineering, Inc.Aqueous chemical leak detection cable
US8256269May 11, 2010Sep 4, 2012Raymond & Lae Engineering, Inc.Aqueous chemical leak detection cable
US8601679Oct 7, 2011Dec 10, 2013Raymond & Lae Engineering, Inc.Twisted leak detection cable
US20110214490 *Mar 2, 2010Sep 8, 2011Masami SakitaWater leak detector
US20120127624 *Aug 4, 2010May 24, 2012Ray RitsonApparatus for delivering an electric shock
EP0980513A2 *Feb 27, 1998Feb 23, 2000Bristol-Myers Squibb CompanyLeak detection system for liquid processing device
EP1499867A1 *Apr 23, 2003Jan 26, 2005Tyco Thermal Controls LLCSensor cable
WO2005054805A2 *Nov 30, 2004Jun 16, 2005Raymond And Lae Engineering InFluid detection cable
WO2006086178A1 *Jan 31, 2006Aug 17, 20063M Innovative Properties CoLiquid leakage sensor
Classifications
U.S. Classification324/522, 324/526, 174/11.00R, 324/525
International ClassificationG08B23/00, G01M3/04, G01M3/16
Cooperative ClassificationG01M3/165, G01M3/045
European ClassificationG01M3/04B2, G01M3/16B
Legal Events
DateCodeEventDescription
Feb 10, 2005FPAYFee payment
Year of fee payment: 12
Apr 16, 2001ASAssignment
Owner name: AMP INCORPORATED, PENNSYLVANIA
Owner name: TYCO ELECTRONICS CORPORATION, PENNSYLVANIA
Free format text: CHANGE OF NAME;ASSIGNOR:AMP INCORPORATED;REEL/FRAME:011682/0568
Effective date: 19990913
Owner name: TYCO INTERNATIONAL (PA), INC., NEW HAMPSHIRE
Free format text: MERGER & REORGANIZATION;ASSIGNOR:RAYCHEM CORPORATION;REEL/FRAME:011682/0608
Effective date: 19990812
Owner name: TYCO INTERNATIONAL LTD., BERMUDA
Owner name: AMP INCORPORATED THE GIBBONS BUILDING 470 FRIENDSH
Owner name: TYCO ELECTRONICS CORPORATION 2901 FULLING MILL ROA
Owner name: TYCO INTERNATIONAL (PA), INC. ONE TYCO PARK EXETER
Owner name: TYCO INTERNATIONAL (PA), INC. ONE TYCO PARKEXETER,
Free format text: MERGER & REORGANIZATION;ASSIGNOR:RAYCHEM CORPORATION /AR;REEL/FRAME:011682/0608
Owner name: TYCO INTERNATIONAL LTD. THE GIBBONS BUILDING 10 QU
Free format text: CHANGE OF NAME;ASSIGNOR:AMP INCORPORATED /AR;REEL/FRAME:011682/0568
Apr 3, 2001ASAssignment
Owner name: AMP INCORPORATED A CORPORATION OF PENNSYLVANIA, PE
Owner name: TYCO ELECTRONICS CORPORATION A CORPORATION OF PENN
Free format text: CHANGE OF NAME;ASSIGNOR:AMP INCORPORATED A CORPORATION OF PENNSYLVANIA;REEL/FRAME:011700/0902
Effective date: 19990913
Owner name: TYCO INTERNATIONAL (PA), INC. A CORPORATION OF NEV
Owner name: TYCO INTERNATIONAL LTD. A CORPORATION OF BERMUDA,
Free format text: MERGER & REORGANIZATION;ASSIGNOR:RAYCHEM CORPORATION A CORPORATION OF DELAWARE;REEL/FRAME:011700/0892
Effective date: 19990812
Owner name: AMP INCORPORATED A CORPORATION OF PENNSYLVANIA THE
Owner name: TYCO INTERNATIONAL LTD. A CORPORATION OF BERMUDA T
Free format text: MERGER & REORGANIZATION;ASSIGNOR:RAYCHEM CORPORATION A CORPORATION OF DELAWARE /AR;REEL/FRAME:011700/0892
Free format text: CHANGE OF NAME;ASSIGNOR:AMP INCORPORATED A CORPORATION OF PENNSYLVANIA /AR;REEL/FRAME:011700/0902
Jan 18, 2001FPAYFee payment
Year of fee payment: 8
Jan 30, 1997FPAYFee payment
Year of fee payment: 4